The alloys used for production of amorphous metals such as those disclosed by Chen et al. in U.S. Pat. No. 3,856,513 are chemically homogeneous and upon subsequent thermo-processing decompose. The decomposition products are a function of the alloy chemistry.
Ray in U.S. application No. 023,379 discloses that the boron containing glasses of the Chen, et al. patent when in powder form can be compacted by standard powder metallurgy techniques. The resulting sintered products contain complex boride particles which are located primarily in the grain boundaries. The Ray application discloses additional alloys not disclosed in the Chen et al. patent which are suitable for formation of boride containing sintered metal parts. However, while the Ray application teaches that amorphous metals could be pulverized and employed as powders to make sintered crystalline parts, many of the alloys suggested by the Ray application when heated decompose by the formation of low melting eutectics. These eutectics can cause incipient melting and make the alloys unsuitable for many powder metal applications (e.g. high temperature applications). Furthermore, the resulting sintered parts have borides with different stoichiometries. The mixture of borides of different stoichsometries depends upon the composition of the alloy. The properties of the borides vary with stoichiometry. The effect of the borides on the properties of the sintered parts is unpredictable unless one can determine the mix of the boride stoichiometries.
The Polk et al. patent, U.S. Pat. No. 4,116,682 discloses a class of boron containing materials which are suitable for forming amorphous metals and not disclosed in the Chen et al. patent. The composition range suggested by Polk, et al. will suffer from the same limitations as those of the Chen et al. patent and the Ray application in that the boride mix and incipent melting point cannot be predicted.
Herold et al. in an article in the Proceedings of Rapidly Quenched Metals III, 1978, entitled "The Influence of Metal or Metalloid Exchange on Crystallization of Amorphous Iron Boron Alloys" discusses the crystallization of amorphous iron boron alloys. In the composition region discussed, the author found different compounds depending on the composition and the thermal processing of the alloy. The study of Herold et al. did not suggest the use of powdered boron containing amorphous metals for powder metallurgy.
While the teachings of the Ray application will allow one to produce sintered parts having borides without necessitating the use of multiple components which must be blended to form the resultant powder, neither the teaching of the Ray application nor this teaching combined with the other teachings on amorphous metal alloys provide a range of compositions which assure freedom from incipient melting during the sintering process.